The invention relates to an improvement of the weighing assemblies of the radial type, that is to say of the type developing with a column or vertical structure comprising at the top a single point for central feeding of the material to be packaged and having as characteristic element a substantial radial symmetry of the various parts which make up this assembly.
This kind of weighing assembly has become established on the market due to its characteristics of speed of feeding the material to be packaged, of restricting overall dimensions on industrial premises and easy approach by the staff controlling the various parts of the weighing device in view of maintenance, repairs and releasing blockages in the feeding of material.
A radial weighing assembly of the type currently known is shown in FIG. 1 attached hereto, where said weighing system, denoted by reference numeral 10, is seen as inserted in a packaging machine, in this case in the form of a bag-filling machine. The known weighing assembly therefore essentially comprises a framework 2 supporting, from the top downwards, a central loading hopper 4 designed to receive from above, for example via a loader 5, said articles 3 to be packaged, and an upper unit 6 for distribution of the articles to be packaged which comprises a plurality of radial channels 8 designed to convey the articles received in a central position from the hopper 4 towards a plurality of weighing baskets, denoted overall by reference numeral 12, placed peripherally and ordered vertically on several weighing levels, designed to define portions of article to be packaged of a preset weight. More particularly said baskets are known as: those of the upper level 12a as prebatching baskets, those of the middle level 12b, which carry out actual weighing of the product, weighing baskets, and those of the lower level 12c as auxiliary baskets.
In traditional weighing assemblies said baskets 12 allow the weighed portions of article to drop into a cone 13 which conveys the "weighed" product to be packaged towards the other units of the packaging machine, denoted overall by reference numeral 14 in FIG. 1. In said conveying cone 13 the product, after a sharp drop onto the highly slanting walls of the cone, converges fast through gravity towards a narrow lower discharge outlet, sliding and rolling along the conical slide surface.
By using the known weighing assembly the articles to be packaged are then moved to the other parts of the packaging machine by means of a filling tube 16, which in the bag-filling machine shown is used to take said predefined portions to be packaged inside, and on the external surface a tubular strip 17 in a heat-sealable plastic material forming the material for making up the packaging bag. Downstream of this filling unit 16 a unit 18 is provided for sealing and cutting the heat-sealable tubular strip whereby actual individual packages of product 19 are formed.
The weighing assemblies of the known type referred above have an operational limit represented by the impossibility of using them to package fragile articles or materials.
By way of an example, by fragile articles we refer for example to products of the food industry, such as for example some types of biscuits and the like which, if subjected to impact and blows, break and crumble easily thus becoming unsuitable for sale to the public. It must nevertheless be understood that each product likely to be broken or damaged following impact comes under the definition of fragile products used here.
The impossibility of using these known weighing assemblies for fragile products is due to the fact that, during the packaging route which occurs progressively from the top downwards, said articles undergo blows and sudden drops which cause breakage or damage thereof.
It has been found that a particularly damaging element for the intactness of fragile articles to be packaged consists of said conveying cone 13 situated below said weighing baskets 12.
At said cone the product, which already falls with a certain violence onto the conical conveying surface thereof, drops virtually freely along the strongly slanting conveying walls of the cone, not therefore undergoing any particular deceleration, but instead accelerating considerably due to the thrust of the force of gravity.
Moreover, as shown in full detail in FIG. 1, the articles 3 forming the weighed portion released by the baskets 12 converge all together towards the lower central discharge outlet of the cone 13 where they collide reciprocally and, due to the large quantity of energy accumulated inside said conveying cone, break and/or crumble. The articles to be packaged then pass, with considerable force due to the high speed accumulated in the cone, to the next filling tube, where due both to further reciprocal colliding and due to the impact along the internal wall of said bag-filling tube 16 and with the packaging in heat-sealable plastic material they are further damaged.
In order to overcome these disadvantages, it is unthinkable to build the conveying cone with walls for sliding of the articles with a small gradient as this would prevent the articles to be packaged from sliding.
Moreover, the use of this conveying cone having a single central discharge for the articles forces weighing assemblies to be built with a single packaging line and moreover such that said packaging units are placed necessarily below said weighing units. The current weighing system with baskets placed peripherally, using said discharge cone, thus heavily restricts the design decisions relating to the arrangement and structuring of the underlying bag-filling units of the packaging machine.
The object of the present invention is therefore that of providing a weighing assembly having an improved system for transporting the articles to be packaged such as to allow packaging without damage even of so-called fragile articles.
More particularly the object of the present invention is that of providing a weighing assembly of the type referred above wherein the use of said conveying cone which causes breakage of the fragile product to be packaged is avoided.
Another object of the present invention is that of providing a weighing assembly structure which is extremely versatile, such as to allow use thereof in association with more than one packaging line, that is to say in association with a packaging line placed in a position other than the central one, unlike the case for weighing devices of the type with radial development known hitherto.